1. Field of the Invention
The present invention relates to an exposure apparatus and a method of manufacturing a device using the same.
2. Description of the Related Art
The manufacture of a TFT substrate and a color filter substrate used for a liquid crystal display device, a substrate used for an organic EL device, or the like includes a step of forming a pattern on a glass substrate according to a photolithographic technique using an exposure apparatus. In recent years, the manufacturing technology for these display panels has progressed with respect to microminiaturization and enlargement. In association with this, large-scale exposure technology has been greatly improved. In particular, improvement in productivity is essential and high illumination intensity of exposure light and processing speed of substrates have dramatically improved.
Conventionally, an exposure apparatus has a light-shielding unit referred to as shutter that controls the shielding and projecting of exposure light emitted from a light source. The light-shielding unit controls carrying out exposure with luminous exposure suitable for element fabrication. The controlled exposure light then exposes a pattern image onto a substrate through a pattern drawn on an original (i.e., a photomask: hereinafter referred to simply as “mask”) or a projection optical system. In addition, exposure processing performed by the exposure apparatus includes an exposure step of performing actual exposure of a substrate, a carry-in step of carrying the substrate into the exposure apparatus, a positioning step of positioning the substrate with respect to the mask, and a carry-out step of carrying the substrate out of the exposure apparatus. The light-shielding unit shields exposure light, and controls it so as not to be irradiated onto the projection optical system such that exposure is not performed in a step other than the exposure step.
The exposure apparatus disclosed in Japanese Patent Laid-Open No. 2001-351850 is a semiconductor manufacturing apparatus provided with a light-shielding unit. By cooling the light-shielding unit that is subjected to irradiation of a large quantity of light, changes in illumination and non-uniform illumination for a short period of time, which are caused by shimmering of air, are obviated. However, in the exposure apparatus having a shutter provided at one place, the temperature in the projection optical system is increased by the energy of exposure light. Heat deformation of the projection optical system and heat distribution in the atmosphere occur due to this temperature increase, resulting in an undesirable change in resolution performance and distortion.
In light of the above, the exposure apparatus disclosed in Japanese Patent Laid-Open No. H03-222405 includes two shutters across a projection optical system. By controlling the opening and closing of these two shutters, the temperature of a projection lens remains constant. However, as shown in FIG. 2 to be described below, the saturation temperature of the projection lens is not always uniform, but changes for each lot, i.e., for each exchange of a mask. It is believed that this is caused by the transmittance of the mask. Therefore, in the exposure method disclosed in Japanese Patent Laid-Open No. H03-222405, a long wait time is required for the temperature of the projection lens to reach the saturation temperature for each exchange of the mask, resulting in longer wait time before the start of exposure.